Turning Prepper – First Project – Solar Dehydrator

Some of my buddies say I have fallen off the deep end. Perhaps I have. But this much I do know: I have an apricot tree that is loaded with fruit this year, and I don’t want them to go to waste. So this is what I built…

SOLAR FOOD DEHYDRATOR

First of all, I would like to give kudos to the OffTheGridNews website for the ideas, in particular video number 2 where engineering students at the University of Wisconsin – Madison build the solar dehydrator that inspired my project. Go watch that video (only a couple minutes long), then come back here for pictures and explanation.

I would also like to make note of the Solar Electricity Handbook that had this nifty Solar Angle Calculator that helped me to figure out what angle my dehydrator needed to be for most of the summer months. I’ll reference this site again later.

Step One: First Frame
Build the first frame with thin (1-1/2″ x 3/4″) furring strips. Use staple gun to hold the rectangle together until you can get the next layer built. CAUTION: As you build these frames, always pre-drill your holes, or your wood screws will split the furring strips!

Measurements for my frame:

(2) 25 3/4″
(2) 34 5/8″

Step Two: Place Sheet Metal
At this point, just lay the sheet metal on the first frame. There should be enough overlap of the metal onto the wood frame that when you screw the frames together in the following steps, that the steel will be secured.

Step Three: Second and Third Frame
Build the second frame with 2×2 furring strips. Use staple gun to hold the rectangle together until you can get the first two frames assembled. Notice in the picture how the frames overlap. Measurements for these 2×2 strips are:
(2) 22 7/8″
(2) 37 1/2″

Build this frame with 2″ screws into the ends (not pictured, will be pictured later). Once this is built, lay it on the metal sheet. Place the plexiglass sheet on top of that, and build a third frame of thin furring strip just like the first one. Make sure everything will line up, and then take the top frame and plexiglass off. You need to screw the first two frames together (holding metal sheet), and paint the inside of the HEAT BOX black, to absorb light/heat. See the next step for assembly, and step five for painting…

Step Four: Assemble bottom portion of Heat Box
You can see here that the first two frames have been screwed together. Sheet metal is ready to paint.

Step Five: Paint the bottom portion of Heat Box
I used high-temp black spray paint (the kind for repainting gas grills) for the interior. Sitting in the sun, it dried VERY quickly. And was it hot? Hot enough to burn you if you touch the back side too long!

Step Six: Assemble the rest of the Heat Box
You can now see the top frame (thin strips), and the plexiglass, attached to the bottom two frames that hold the blackened sheet metal.

Measurements:
(2) 4 foot lengths
(2) 22 7/8″ lengths
Overlap of long sides: 5 1/4″ each end. (NOTE: If you want to build an adjustable box (different angles for different times of the year), you MUST make this overlap longer… therefore make the long sides longer than 4 foot.)

Step Eight: Attach Base to Dehydrator Box Frame
Attach plywood to box frame as pictured. What is NOT pictured here are the airflow holes I drilled in the plywood at the end that would become the lowest portion of the dehydrator.

Measurements:
(1) 26″ x 37 1/2″

Step Nine: Build posts and attach to Box Frame
This step caused me the most trouble. And because of that, I forgot to get pictures of it until I was already done. Let me explain…

First of all, I spent some time online looking for information on what angle to set the dehydrator. I discovered that the angle changes for all latitudes depending on the time of the year. So… I figured out I needed one angle for summer (June 21st), and a different angle for fall (September 21st). In my first post, I drilled one set of holes for summer, and another set of holes for fall. I figured out that the overlap I had on my box frame was not quite sufficient to get a set of holes for winter. The angle would be 24 degrees, and much too steep for the box to attach properly. I should have made my box long sides… longer!

In the end, I forgot to drill the holes for my “fall setting” in the other three legs, and so I just put the legs on, giving my box a 72 degree slope.

Also in this picture: Hinges on the Heat Box (attached), and venting holes. There are three of them, two which are hidden by the legs. I may need to make these bigger, but when I put a digital thermometer in the middle vent hole, after the box was in the sun for a while, it read 126-128 degrees. According to the engineering students in the video you watched, the ideal temps are 120-140 degrees. So I need to get my box a little warmer… I am hoping the black paint will fix that.

Step Ten: Build posts and attach to Box Frame
Same step as last time… just the front view.

Step Eleven: Build posts and attach to Box Frame
Same step as last time… just the inside view.

Step Twelve: Inside Drying Trays
I confess… I forgot to get pictures and measurements of the removable drying trays while I built them. I am very sorry! Let me describe them to you…

Using the same method as the heat box, the two drying trays (you could build four, and double stack them) use one frame of thin strips, and one frame of 2×2 strips. What you see in this picture is two trays. The only reason there is a divider in the center of each tray is because the “screen” I bought at Bed Bath And Beyond came in two sizes. I used the bigger square on the left, and the smaller rectangle on the right. Consequently, the trays are probably stronger this way. Remember to pre-drill all your holes!

The vertical pieces of wood you see at the bottom are simply spacers. I’ll probably leave them in there for better air circulation. Underneath the two drying trays are 2x2s that edge the entire bottom-inside of the box, to get the drying trays up in the air. You can barely see one of them in the lower right corner on this picture.

Once those were built (sorry, I don’t have measurements… you’ll probably want to measure these for yourself once your dehydrator box is built so you don’t get the drying trays in there too tight), I painted the entire unit, taking care to NOT paint the reflective metal on the underside of the Heat Box, or the plexiglass on the top of the Heat Box.

More Pictures
I’ll have to let you know how this turns out. I think I’ll have to set this thing in the sun a few days to drive all the moisture and chemical smell out of the treated lumber and paint before I can use the dehydrator. Hopefully my airflow holes are large enough. If not, I’ll drill them again. You may notice some fancy additions… the handle on the front came from an old grill. Same with the temperature gauge on the back (I’ll probably replace that with a digital model).

And I do have TWO MORE STEPS that are not done yet. I’m going to have to use window screen on the underside of the plywood (near the front), and the back frame (pictured below) to block insects from coming into the box. Also, I may need to put some thin weather stripping around the edge of the frame so when the Heat Box sits down, a tighter seal is formed.

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FOR MY READERS: As you can see, I am taking a little break from fiction writing. Summer is here, and I’ve had a lot to do. I’ll try to get back to my work-in-progress (Heaven’s Garden, book two in The Chronicles of Gan) at the end of the summer. Thanks for your patience!